1. Field of the Invention
The present invention relates to a rechargeable battery module, and more particularly, to a rechargeable battery module having a plurality of unit batteries and interposed barriers.
2. Description of the Related Art
Unlike a primary battery, the rechargeable battery may be recharged. Lower power batteries are used for various portable electronic devices such as cellular phones, laptop computers, and camcorders. Bulk size batteries are used as the power source for motor drive, such as in hybrid electric vehicles.
Depending on the external shape, rechargeable batteries may be classified into different types, for example, prismatic and cylindrical batteries. When they are used for motor drive of the machines requiring a high power source such as the hybrid electric vehicles, the rechargeable batteries may form a rechargeable battery module of high power.
The rechargeable battery module is formed by serially connecting several rechargeable batteries (hereinafter “unit batteries”), and each of the unit batteries includes an electrode assembly in which a separator is interposed between a positive electrode and a negative electrode. The electrode assembly is inserted inside a case, and a cap assembly is assembled with the case to seal the case. The cap assembly can include terminals disposed extending from the inside to the outside of the case and electrically connected to the positive electrode and the negative electrode, respectively.
If the unit batteries are prismatic type batteries, the unit batteries are arranged to alternate positive and negative terminals of one unit battery projected from the upper portion of the cap assembly with the positive and negative terminals of an adjacent unit battery. Adaptors of the electric conductor are typically mounted on the threaded negative and positive terminals such that they are electrically connected with each other to form the battery module.
Since the battery module connects several to tens of unit batteries to form one battery module, there is a need to efficiently dissipate heat generated from each unit battery. In particular, when the unit battery is used as bulk size rechargeable batteries for motor drive such as in electric vehicles, hybrid electric vehicles, motor scooters, and vacuum cleaners, the heat dissipation is of significant importance.
If the heat dissipation does not occur properly in the battery module, the temperature of the battery module may excessively increase due to the heat generated from each unit battery, and accordingly, not only the battery module but also the machines with the battery module, can malfunction.
Accordingly, when forming the battery module, a barrier is disposed between unit batteries, and the space between unit batteries formed by the barrier is used not only for cooling unit batteries but also for preventing distortion due to heat expansion of the unit batteries.
To perform such functions, the barrier needs sufficient strength, and structure for efficient heat dissipation.
However, the barriers in the conventional rechargeable battery module do not satisfy the above two conditions simultaneously so there is difficulty in forming rechargeable battery modules of the quality which consumers expect.
That is, if the barriers ensure the sufficient strength, its manufacturing cost is increased and there is restriction in designing a passage of cooling air. Alternatively, if the barriers are formed having high cooling efficiency, they tend to exhibit structural weakness.
Furthermore, the barrier has to be manufactured using a die casting method rather than an injection molding method so as to ensure an improved strength. The barriers fabricated using the die casting method are hard to weld to cause difficulty of a rechargeable battery module constitution.